It is known in the art that photographic display materials are utilized for advertising, as well as decorative displays of photographic images. Since these display materials are used in advertising, the image quality of the display material is critical in expressing the quality message of the product or service being advertised. Further, a photographic display image needs to be high impact, as it attempts to draw consumer attention to the display material and the desired message being conveyed. Typical applications for display material include product and service advertising in public places such as airports, buses and sports stadiums, movie posters, and fine art photography. The desired attributes of a quality, high impact photographic display material are a slight blue density minimum, durability, sharpness, and flatness. Cost is also important, as display materials tend to be expensive compared with alternative display material technology, mainly lithographic images on paper. For display materials, traditional color paper is undesirable, as it suffers from a lack of durability for the handling, photoprocessing, and display of large format images.
In the formation of color paper it is known that the base paper has applied thereto a layer of polymer, typically polyethylene. This layer serves to provide waterproofing to the paper, as well as providing a smooth surface on which the photosensitive layers are formed. The formation of a suitably smooth surface is difficult, requiring great care and expense to ensure proper laydown and cooling of the polyethylene layers. The formation of a suitably smooth surface would also improve image quality, as the display material would have more apparent blackness as the reflective properties of the improved base are more specular than the prior materials. As the whites are whiter and the blacks are blacker, there is more range in between and, therefore, contrast is enhanced. It would be desirable if a more reliable and improved surface could be formed at less expense.
Prior art photographic reflective papers comprise a melt extruded polyethylene layer which also serves as a carrier layer for optical brightener and other whitener materials, as well as tint materials. It would be desirable if the optical brightener, whitener materials and tints, rather than being dispersed a single melt extruded layer of polyethylene, could be concentrated nearer the surface where they would be more effective optically.
Prior art photographic display materials historically have been classified as either reflective or transmission. Reflective display materials typically are highly pigmented image supports with a light sensitive silver halide coating applied. Reflective display materials are typically used in commercial applications where an image is used to convey an idea or message. An application example of a reflective display material is product advertisement in a public area. Prior art reflective display materials have been optimized to provide a pleasing image using reflective light. Transmission display materials are used in commercial imaging applications and are typically backlit with a light source. Transmission display materials are typically a clear support with an incorporated diffuser coated with a light sensitive silver halide emulsion. Prior art transmission display materials have been optimized to provide a pleasing image when the image is backlit with a variety of light sources. Because prior art reflective and transmission products have been optimized to be either a reflection display image or a transmission display image, two separate product designs must exist in manufacturing and two inventories of display materials must be maintained at the commercial printer. Further, when the quality of the backlighting for transmission display material is reduced when, for example, a backlight burns out or the output of the backlight decreases with the age, the transmission image will appear dark and reduce the commercial value of the image. It would be desirable if an image support could function both as a reflection and transmission display material.
Prior art transmission display materials use a high coverage of light sensitive silver halide emulsion to increase the density of the image compared to photographic reflective print materials. While increasing the coverage does increase the density of the image in transmission space, the time to image development is also increased as the coverage increases. Typically, a high density transmission display material has a developer time of 110 seconds compared to a developer time of 45 seconds or less for photographic print materials. Prior art high density transmission display materials, when processed, reduce the productivity of the development lab. Further, coating a high coverage of emulsion requires additional drying of the emulsion in manufacturing, reducing the productivity of emulsion coating machines. It would be desirable if a transmission display material was high in density and had a developer time less than 50 seconds.
Prior art reflective photographic materials with a polyester base use a TiO.sub.2 pigmented polyester base onto which light sensitive silver halide emulsions are coated. It has been proposed in WO 94/04961 to use an opaque polyester containing 10% to 25% TiO.sub.2 for a photographic support. The TiO.sub.2 in the polyester gives the reflective display materials an undesirable opalescent appearance. The TiO.sub.2 pigmented polyester also is expensive because the TiO.sub.2 must be dispersed into the entire thickness, typically from 100 to 180 .mu.m. The TiO.sub.2 also gives the polyester support a slight yellow tint which is undesirable for a photographic display material. For use as a photographic display material, the polyester support containing TiO.sub.2 must be tinted blue to offset the yellow tint of the polyester, causing a loss in desirable whiteness and adding cost to the display material. It would be desirable if a reflective display support did not contain any TiO.sub.2 in the base and could be concentrated near the light sensitive emulsion.
Prior art photographic display materials use polyester as a base for the support. Typically the polyester support is from 150 to 250 .mu.m thick to provide the required stiffness. A thinner base material would be lower in cost and allow for roll handling efficiency, as the rolls would weigh less and be smaller in diameter. It would be desirable to use a base material that had the required stiffness but was thinner to reduce cost and improve roll handling efficiency.